n. Contrary to subway stalactite, subway stalagmite does not form on the ceiling. Subway stalagmite is a deposit left by dripping sewer water or run-off that comes from the stalactite deposits on subway ceilings. Usually it is a lighter color, though it ranges from white to brown, and gives off a foul odor. This can be attributed to the fact that it’s on the floor, below your nose, where air can circulate up to your nose. These are generally flat, and do not develop as tall or as quickly as subway stalactite.

A white to brown flat deposit below a dripping sewer pipe that gives off a foul odor can be considered subway stalagmite.